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Rac2 in Th1 Cells

Immune responses can be mediated by cells (cell-mediated immunity) or through circulating factors like antibodies (humoral immunity), depending on whether naive T cells differentiate into T helper 1 (Th1) or T helper 2 (Th2) cells. Li et al. report that the small guanosine triphosphatase Rac2 increased the expression of interferon γ (IFNγ), a cytokine that promotes T cell differentiation, and that it appeared to signal through the mitogen-activated protein kinase p38 and the transcription factor NF-κB.